Master Naturalists: Sea level changes along Gulf Coast a real concern

By By Paul and Mary Meredith
April 5, 2012 at midnightUpdated April 4, 2012 at 11:05 p.m.

Some other sea-level information

Florida has 2.4 million people living less than four feet above current high tide - almost 13 percent of Florida's current population. Grand Isle, La., (elevation 7 feet) is expected to have a 19-inch rise (90 percent chance of a 14- to 27-inch rise) by 2050.

In some ways, we're lucky now. Lucky in the sense that we now have enough data to understand how sea-level changes can affect our rich coastal area. Until now, there has been a lot of conjecture about what is going on, but no really good scientific data about how rising sea levels can affect our area.

Facts from sea-level science - continental tilting

The science of sea-level change is geological, meteorological, physical and hydrological.

Although our house seems stable, it's actually sinking slowly, just like the rest of the western Gulf, which is settling after northern continental areas were pushed down during the last Ice Age, and we were pushed up.

It's like putting weight in a bowl of Jell-O. Jell-O that is pushed down by weight domes up elsewhere. Remove the weight and the pushed-up area falls.

Melting ice, glaciers

Also, the entire ocean pool is rising for several reasons. First, water stored as ice is melting as the climate warms.

Glaciers, plus continental and polar ice caps, are melting and breaking off and floating to warmer areas where they melt. Global sea-level rise (roughly 8-inch rise since the 1880s) is increasing at a rate unmatched in more than 2,000 years - but why?

It's warmer worldwide, especially at the poles.

Water warming

Water expands as it warms. Because water on our coastal shelf warms faster than the ocean as a whole (because of shallow depths and local currents, for example), our water is expanding faster - above the average.

Finally, if the Gulf Stream, which currently draws water away from our shoreline, slows as the climate warms, the net effect will be that water will pile up behind it, rather like a traffic jam, increasing Gulf and coastal sea levels.

No, but respected oceanographers see a strong chance there will be.

What is the net effect?

According to the nonprofit Climate Central's Surging Seas Report on sea-level change, Rockport's sea level rose 12 inches between 1948 and 2000 and their recently-released forecasts predict another 14-inch rise (90 percent chance of 10- to 22-inch rise) by 2050.

That means a 20 percent chance of a 100-year flood (6.1 feet) from combined tides and a storm surge, instead of 15 percent chance of the same flood without the rise (33 percent increase in risk).

And it's worse in Galveston. They're expecting a 16-inch rise (90 percent chance of 14- to 26-inch rise) and 50 percent increase in the likelihood of a 100-year flood.

Should we be concerned?

Yes, we should. Our coast will be immersed more often. At risk will be more than 161,000 people, 95,000 residences and 979,000 acres of valuable Texas coastal land.

The 10 Texas counties with the largest total exposed populations (listed most population to least), according to the Surging Seas Report, are Jefferson, Galveston, Brazoria, Nueces, Orange, Harris, Cameron, Aransas, Calhoun and Matagorda. For more information on the scientific basis for this article, see Climate Central's website, www.climatecentral.org. In addition to the scientific articles, they have an interactive graphic model, which gives their forecasts down to zip-code level of detail.

Paul and Mary Meredith are master naturalists. Contact them at paulmary0211@sbcglobal.net.